The present invention relates generally to a motorcycle automatic transmission, and more particularly to an automatic retrieving structure of sliding transmission disk of the motorcycle automatic transmission.
A prior art motorcycle engine is generally composed of a starting device provided with a sliding drive disk 1, as shown in FIGS. 1-3. The rotation of the sliding drive disk 1 causes a plurality of rollers 3 to roll outwards in an arcuate manner in conjunciton with a drive disk 5 to control the speed of a drive belt 4 and the sliding interval of the sliding drive disk 1, so as to impart the driving power to the transmission device. Before the engine is started, the sliding drive disk 1 is located by a bevel plate 2 while the driving end of the drive belt 4 is retained on a drive disk wheel nave 6 located between the sliding drive disk 1 and the dvive disk 5. As shown in FIG. 4, the transmission end of the drive belt 4 is retained on the outer ring disk wall of the transmission disk 7 and the sliding transmission disk 8. The trasmission disk 7 has a transmission nave 71 while the sliding transmission disk 8 has a shaft sleeve 81 fitted over the transmission nave 71 for retaining the drive belt 4. As shown in FIG. 5, the shaft sleeve 81 of the sliding transmission disk 8 is provided with a spring seat 82 having at the bottom thereof a receiving frame 821 for disposing therein a compression spring 9 for forcing the sliding transmission disk 8 to be close to the transmission disk 7 so as to permit the transmission end of the drive belt 4 to be retained on the outer disk wall for preparing to actuate at a low speed and a high torsion. As a result, the starting device is able to actrate the transmision device at a low speed and a high torsion at such time when the engine is started. As the engine is accelerated, the sliding drive disk 1 is pushed gradually toward the drive disk 5 by the moment of inertia of the rollers 3 which are caused to move along an arcuate recess 11 toward the disk circumferential ring, thereby causing the driving end of the drive belt 4 to disengage the driving disk wheel nave 6 and to become retained gradually on the outer disk surfaces of the sliding drive disk 1 and the drive disk 5, as shown in FIGS. 3 and 6. As the interval between the sliding drive disk 1 and the drive disk 5 is shortened, the drive belt 4 is caused to move further close to the outer circumferential ring of the side disk surface in view of the fact that the transmission wheel nave 71 is provided with a protruded pin member 72, and that the shaft sleeve 81 of the sliding transmission disk 8 is provided with a pin slot 811 opposite in location to and engageable with the protruded pin member 72. In the meantime, the transmission end of the drive belt 4 is caused to cooperate with the dispplacement of the sliding drive disk 1 to enable the sliding transmission disk 8 to move in the same direction so as to compress the compression spring 9 for increasing the interval between the sliding transmission disk 8 and the transmission disk 7. As a result, the drive belt 4 is caused to move inwards toward the transmision wheel nave 71 for actuating at a high speed. As the speed of the motorcycle is reduced, the sliding transmission disk 8 is caused to move toward the transission disk 7 by the rebounding tension of the compression spring 9 so as to cause the transmission end of the drive belt 4 to disengage the transmission wheel nave 71 to move toward the outer disk wall. In the meantime, the transmission end is caused to move toward the drive disk wheel nave 6, thereby causing the rollers 3 to retrieve in preparing for the motorcycle to accelerate again.
On the basis of the description presented above, it is readily apparent that the acelerated motion of the motorcycle is dependent on the rebounding tension of the compression spring 9, and that the accelerated motion of the motorcycle is bound to fail if the response of the rebounding tension of the compression spring 9 is poor, or if the magnitude of the rebounding tension of the compression spring 9 is inadequate.
As shown in FIG. 7, various component parts and the compression spring 9 of the prior art motorcycle are packed together. As a result, the interval between the sliding transmission disk 8 and the transmission disk 7 is gradually increased as the motorcycle is accelerated gradually, thereby resulting in a greater compression of the compression spring 9. Therefore, the compression spring 9 is vulnerable to failure in providing an effective rebounding tension after the motorcycle is decelerated or braked.